JPH04213902A - Cooled waveguide - Google Patents

Abstract

PURPOSE: To reduce the loss per unit length by easily and inexpensively cooling a waveguide to reduce the resistivity of a conductor. CONSTITUTION: The waveguide is cooled by circulation of a cooling fluid which can be compatible with microwave transmission. Therefore, the waveguide is provided with a supply tube 3 and a discharge tube 4 which are placed near closed windows 5 and 6 which close the waveguide in end parts of the waveguide. These tubes are placed in such area that they don't interfere in electromagnetic propagation. A jacket 7 surrounds the waveguide and is separated from the waveguide by a spacer 8. A space 9 between the jacket and the waveguide is either vacuous or filled with heat insulating materials. The transmission characteristic of the waveguide is improved by the temperature reduction.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to the cooling of waveguides.

0002

BACKGROUND OF THE INVENTION Cooling of microwave waveguides is necessary when a significant reduction in losses per unit length is desired.

The purpose of lowering the temperature of the superconducting material below the critical temperature is to lower the temperature of the aluminum constituting the outer tube of the waveguide, as well as to lower the temperature of the conductor, which is the main parameter that determines the loss per unit length. This is to significantly reduce resistivity. Therefore, the loss per unit length of an aluminum rectangular waveguide at 20°C in the X band (10 GHz) is 12 dB.
/100m. These losses are 3 at liquid nitrogen temperature.
．． 2dB/100m, and 0.4dB/100m at liquid hydrogen temperature.
The distance decreases to 100m.

[0004] The superconducting properties of certain materials have also been used to considerably reduce the resistivity at microwave frequencies of the conductive outer tube that makes up the waveguide, thereby considerably reducing losses per unit length. obtain.

In existing cooling systems, cooling is accomplished by circulating liquid nitrogen within a sheath that is independent of and surrounds the waveguide structure. Such devices are complex and difficult to apply.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to cool waveguides more easily and inexpensively than existing devices.

[0007] The present invention relates to a cooled waveguide with a sealed window at each end, the waveguide being cooled by a cooling fluid circulating within the waveguide and for this purpose having a supply pipe and a discharge pipe. , characterized in that the tubes are located at opposite ends of the waveguide, and each tube is located in an area that does not interfere with electromagnetic propagation of the waveguide. The cross section of the waveguide can be oval, oval, circular or square. However, it is preferred that the waveguide has a rectangular cross section consisting of two large sides, each tube being arranged on each large side.

[0008] Each tube is located near each sealing window.

The waveguide may be surrounded by a jacket that is spaced from the waveguide by a spacer to provide space between the waveguide and the jacket.

Preferably, the space between the jacket and the waveguide is filled with a thermally insulating material.

Preferably, the space between the jacket and the waveguide is a vacuum to ensure thermal insulation.

Preferably, each tube is secured at its distal end with a sealed window. This distal end is capped at the end of the waveguide. The waveguide includes an opening located on the tube to allow cooling fluid to circulate within the waveguide.

Preferably, each tube is secured at its distal end with a sealed window. This distal end is capped at the end of the waveguide. The waveguide includes an opening located on the tube to allow cooling fluid to circulate within the waveguide. The jacket is also fixed to the distal end in a sealed manner.

[0014] Advantageously, the cooling liquid is a liquefied gas.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a rectangular waveguide having a small side 1 and a large side 2 and closed at each end by a sealed window 5, 6 of known type. Each end of the waveguide terminates in a connecting flange 11. The waveguide has a tube 3 on each of its large faces 2 for circulation of cooling fluid within the waveguide.
, 4. These tubes are preferably located at each end of the waveguide in areas that do not interfere with the waveguide, so as not to interfere with electromagnetic propagation within the waveguide. In the case of a rectangular waveguide as shown in Figure 1, the tube is
are arranged according to the XX' axis.

In this case, the waveguide cooling device consists of two tubes 3 and 4 in its simplest form. The waveguide is not limited to the rectangular structure shown as an example, but may be of any shape including square, rectangle, oval, circle, or oval.

Since a cooling fluid exists within the waveguide, the dimensions of the waveguide at the electric surface and the wavelength λg within the waveguide are expressed as follows:

[0019]

[Math 1] It is influenced by the dielectric constant of the liquid with a ratio expressed as .

[0020] The cooling liquid is advantageously a liquefied gas.

In the case of liquid nitrogen in the range of 63.3K to 78K, the dielectric constant hardly changes from 1.432 to 1.475.

Since the resistivity ρ of the metal constituting the waveguide is very small, the Q is much higher than would normally be obtained with a cavity of the same type that is not cooled by injection of liquefied gas.
It is possible to manufacture a resonant cavity with .

The pipe 3.4 in FIG. 1 is of course connected to a liquefied gas installation. For example, a liquefied gas tank to which a liquefied gas supply pipe 3 is connected may be used. The exhaust pipe 4 is connected to the atmosphere, for example. The liquefied gas is discharged through the pipe 4, of course at a very low flow rate. Generally, liquefied gas flows slowly within the waveguide.

FIG. 2 shows a variant of the cooled waveguide of the invention. In this figure, for example, the waveguide of FIG. 1 is insulated from the outside by a jacket 7 that has the same shape as the waveguide and is slightly larger than the waveguide. Spacer 8 serves to maintain a space 9 between the jacket and the waveguide. The jacket 7 can be made of metal, plastic or composite material, for example. The spacer 8 consists, for example, of a helical rod, preferably made of a heat-insulating material. Connection flange 11 has fixing hole 1 to the same type of flange.
It has 3.

The space 9 between the jacket 7 and the waveguide is filled with a heat insulating material, for example. A vacuum can also be created within this space in order to limit heat loss and thus optimize the thermal insulation.

FIG. 3 shows the end of the waveguide of the invention in its simplest embodiment as shown in FIG. The distal end consists of a sleeve 10, a sealing window 6 and a tube 4. The hermetic window is fixed in a known manner to one end of the sleeve 10, which has a slightly larger cross-section than the waveguide whose end is capped by the sleeve 10. In the case of a rectangular waveguide, the tube 4 is fixed in the center of the large surface of the sleeve and is located over an opening provided in the large surface of the waveguide. Of course, the sleeve is fixed on the waveguide in a hermetically sealed manner.

FIG. 4 shows a modification of the distal end of FIG.

In the case of FIG. 4, the distal end is fitted with a tube 4 on the large side of the sleeve 12 of the flange, which is provided with a sealing window 6 and a hole 13 for connection with a flange of the same type. This is the flange 11. As in FIG. 3, the tube 4 rests over an opening provided in the large plane of the waveguide when the flange is crowned on the end of the waveguide. Of course, the sleeve 12 is fixed hermetically over the waveguide.

FIG. 5 shows a variation of the end section used in the cooled waveguide of FIG. The distal end consists, for example, of a sleeve 10 and a sealing window 6 as in FIG.

[0030] The jacket 7 (in Fig. 2) is designed so that a vacuum can be created in the space 9 between the jacket 7 and the waveguide.
It is fixed to the shoulder 14 in a sealed manner. Of course, the end portion of FIG. 5 may be the same as the end portion of FIG. 4. In this case, the sleeve 12 includes the shoulder 14 of FIG.

The embodiments shown and described are in no way limiting and the waveguides may be of any form and size, whether made of metal (eg aluminum) or of superconducting material. , or coated with a superconducting material, are of course merely illustrative of the invention as it applies generally to waveguides.

[Brief explanation of the drawing]

1 is a schematic illustration of a cooled waveguide of the invention with rectangular cross section, suitable for thermal isolation; FIG.

FIG. 2 shows a modified example of the cooled waveguide of the invention.

FIG. 3 shows a distal end of a cooled waveguide of the present invention.

FIG. 4 is a diagram showing a modification of the distal end of FIG. 3;

FIG. 5 shows a variation of the distal end for use in a cooled waveguide such as that shown in FIG. 2;

[Explanation of symbols]

3,4 pipe 5, 6 Sealed window 7 Jacket 8 Spacer 9 Space 10,12 Sleeve 14 Shoulder

Claims (9)

[Claims] 1. A cooled waveguide having a sealed window at each end, the waveguide being cooled by a cooling fluid circulating within the waveguide and for which a supply pipe and a discharge pipe are connected. tubes, the tubes being disposed at opposite ends of the waveguide, and each tube being located within an area of the waveguide that does not interfere with electromagnetic propagation. 2. Waveguide according to claim 1, characterized in that it has a rectangular cross section with two major faces and each tube is located on each major face. 3. Waveguide according to claim 1, characterized in that each tube is located near each sealing window. 4. The waveguide of claim 1, wherein the waveguide is surrounded by a jacket that is separated from the waveguide by a spacer to provide a space between the waveguide and the jacket. 5. The waveguide according to claim 4, wherein the space is filled with a heat insulating material. 6. The waveguide according to claim 4, wherein the space is a vacuum. 7. Each tube is provided with a sealed window and fixed at a distal end that is crowned to the end of the waveguide, and the waveguide is adapted to circulate a cooling fluid within the waveguide. 4. A waveguide according to claim 3, characterized in that it comprises an opening located on the tube. 8. Each tube has a sealed window and is secured to a distal end that is crowned to the end of the waveguide, the waveguide having a tube for circulating a cooling fluid within the waveguide. 5. The waveguide of claim 4, further comprising an overlying opening and wherein the jacket is sealingly secured to the distal end. 9. The waveguide according to claim 1, wherein the cooling fluid is a liquefied gas.